Summary of work: The goal of this study is to assess the predictive value of distortion product otoacoustic emissions (DPOAEs) to identify physiologic changes in hair cell function in humans exposed to acoustic overstimulation. It is hypothesized that acoustic overstimulation will result in decreased amplitude of DPOAEs. Noise exposure is known to cause a temporary decrease in hearing which appears to share common changes in cochlear physiology, such as temporal growth and recovery patterns. Resonant frequency of the outer ear has also been implicated in the magnitude of the temporary hearing loss. The secondary hypothesis states that the frequencies at which DPOAEs show maximum amplitude decrease will correspond to the resonance characteristics of the outer ear. Seven normal volunteers ranging in age from 22-29 years (mean = 23 years) have been evaluated. Repeatable responses have been recorded from all subjects and predictable decreases in DPOAE amplitude are seen. Data collection is ongoing and will continue until 12 subjects are seen.